Multi-Subject Competition

Description:

Input:

The first line contains two integers $$$n$$$ and $$$m$$$ ($$$1 \le n \le 10^5$$$, $$$1 \le m \le 10^5$$$) — the number of candidates and the number of subjects.

The next $$$n$$$ lines contains two integers per line: $$$s_i$$$ and $$$r_i$$$ ($$$1 \le s_i \le m$$$, $$$-10^4 \le r_i \le 10^4$$$) — the subject of specialization and the skill level of the $$$i$$$-th candidate.

Output:

Print the single integer — the maximum total sum of skills of delegates who form a valid delegation (according to rules above) or $$$0$$$ if every valid non-empty delegation has negative sum.

Sample Input:

6 3
2 6
3 6
2 5
3 5
1 9
3 1

Sample Output:

22

Sample Input:

5 3
2 6
3 6
2 5
3 5
1 11

Sample Output:

23

Sample Input:

5 2
1 -1
1 -5
2 -1
2 -1
1 -10

Sample Output:

0

Note:

In the first example it's optimal to choose candidates $$$1$$$, $$$2$$$, $$$3$$$, $$$4$$$, so two of them specialize in the $$$2$$$-nd subject and other two in the $$$3$$$-rd. The total sum is $$$6 + 6 + 5 + 5 = 22$$$.

In the second example it's optimal to choose candidates $$$1$$$, $$$2$$$ and $$$5$$$. One person in each subject and the total sum is $$$6 + 6 + 11 = 23$$$.

In the third example it's impossible to obtain a non-negative sum.